Ribbon blown glass envelopes have been traditionally formed on a ribbon machine with two-part molds having a partible construction and which rotate while encircling a hollow molten glass blank. Said conventional glass molds have been generally provided with a paste coating of the central mold cavity along with vent openings to form a steam cushion against which the glass envelope is blown while said mold halves are rotating. Although the bulb portion of a glass envelope blown in the conventional manner has included cylindrical as well conical and spherical shapes, all of these shapes terminated at the closed end of the bulb portion in a spherical contour preventing the blown article from physically supporting itself. Accordingly, such limitation has retarded any wider utilization of conventional ribbon blown glass envelopes in a variety of end product applications including liquid containers and even lamp glass envelopes requiring a relatively flat face portion to serve as a lens member in the lamps.
The present invention relates to novel means whereby glass articles of various types are blown on a ribbon machine in a novel mold construction which shapes the closed end of the glass envelope to provide a self-supporting base contour. More particularly, said novel mold construction includes three basic parts which cooperate in forming a bulb shape terminating in a flattened contour sufficient to permit the glass envelope to be self supporting, that is to stand alone without additional physical support. The basic mold design of the present invention includes a pair of cooperative partible halves forming the sides of the blown glass envelope in a central cavity and which further includes a separate base part located at the lower end of said cavity to shape the closed end of said blown glass envelope into the desired self-supporting contour, said base part of the mold being provided with reciprocal motion in a vertical direction.
Accordingly, an important object of the present invention is to provide a ribbon blown glass envelope having assorted shapes for various end product application wherein the bulb portion of said envelope terminates in a self-supporting contour.
Another important object of the present invention is to provide ribbon blown glass envelopes having either curved or planar sides together with an integral self-supporting base contour which can also be planar or curved in shape.
Still another important object of the present invention is to provide an improved method for manufacture of said novel glass envelope on a ribbon machine by means of a novel mold design.